PMNs are composed of three cell types; neutrophils, eosinophils and basophils, based on their staining characteristics with certain dyes.
Also called granulocytes since they consist of many granules consisting lytic enzymes.
These cells are predominantly important in the removal of bacteria and parasites from the body.
They engulf these foreign bodies and degrade them using their powerful enzymes.
Multi-lobed nucleus, 11-14 μm
50-70% of circulating WBC (higher numbers suggestive of bacterial infection)
7-10 hours in circulation and then migrate to tissue, life 3-4 days
The fine granules stain poorly with acidic and basic dyes neutrophil.
Phagocytosis and killing of ingested microorganisms.
Granules contain bactericidal enzymes; eg. Lysozyme, myeloperoxidase; neutral proteases (i.e. elastase); acid hydrolases (B-glucoronidase), collagenase and lactoferrin and cathepsin B.
The phagosome fuses with granules to destroy internalized bacteria by oxygen dependent respiratory burst.
Neutrophils are the 1st cells to arrive. A number of substances produced during an inflammatory response recruit neutrophils to a site of inflammation.
Represent 1-3% of circulating WBCs, 11-15 μm
Possess a bi-lobed nucleus and a heavily granulated cytoplasm.
Granules stain orange/red with the acidic dye Eosin Y.
Somewhat phagocytic but DO NOT act as APCs.
The major role of the eosinophil is believed to be against parasites, particularly parasitic worms.
Eosinophils kill by ADCC [antibody dependent cell-mediated cytotoxicity] by binding to parasite – specific IgE via cell surface
When eosinophils bind to IgE on the surface of a worm, the cell is triggered to degranulate. The contents of the granules cause
damage to the worm’s tegument.
One component unique to the eosinophils – and highly toxic to worms – Major Basic Protein (MBP).
Only present in the bloodstream, and represent 0.2 % of circulating WBC
Lobed nucleus – more variable, large coarse granules stain blue with basic dye methylene blue.
They play a major role in the allergic response when they release their granules (containing histamine, serotonin, heparin, prostaglandin, etc into the bloodstream following exposure to specific allergens).
Basophils bear Fc receptors for IgE (FceRs)
When an individual is exposed to an allergen, allergen specific IgE is produced. This IgE binds to the surface of basophils [in the sensitization phase of the allergic response].
Upon re-exposure to the allergen, the allergen binds to IgE on the surface of basophils resulting in degranulation [effector phase].
Binod G C
I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.
View all posts by Binod G C